British middleweight Martin Murray knocked down WBC champion Sergio Martinez before losing to the Argentine on a unanimous points decision.
Murray, 30, floored Martinez in the eighth round and also had his rival on the canvas in the 10th, although the referee ruled the latter was a slip.
Martinez, 38 rallied late on in Buenos Aires and won the bout 115-112 on the cards of all three judges.
It is Murray's first defeat and he will come again. If Birmingham's Matthew Macklin can dethrone WBA champion Gennady Golovkin in June, and with Londoner Darren Barker standing by, we could finally have the Benn-Eubank-Watson-style middleweight tournament we have been denied for so long.
The defeat was Murray's first defeat in 27 fights.
But, despite the loss, the St Helens boxer enhanced his reputation after giving his more established opponent, who has 51 wins from 55 fights, a tough contest.
In front of a 40,000 crowd at the Estadio Jose Amalfitani, Martinez was the aggressor at the start of the fight as Murray began cautiously.
The challenger upped his work rate in rounds five and six, which left Martinez bleeding from his left eye.
The champion took round seven before a left hook to the jaw and a solid right in the eighth sent the backpedalling Martinez tumbling to the canvas.
The Argentine responded by giving Murray a bloody nose in the ninth and, despite again being floored in the next after good work by Murray, referee Massimo Barrovecchio ruled a slip as incessant rain fell.
Martinez again recovered to finish the fight strongly to claim a hard-fought victory.